/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

#ifndef PEBBLE_DR_REFLECTIONLOCAL_H
#define PEBBLE_DR_REFLECTIONLOCAL_H

#include <stdint.h>
#include <cstring>
#include "framework/dr/protocol/protocol.h"

/**
 * Local Reflection is a blanket term referring to the the structure
 * and generation of this particular representation of Thrift types.
 * (It is called local because it cannot be serialized by Thrift).
 *
 */

namespace pebble { namespace dr { namespace reflection { namespace local {

using pebble::dr::protocol::TType;

// We include this many bytes of the structure's fingerprint when serializing
// a top-level structure.  Long enough to make collisions unlikely, short
// enough to not significantly affect the amount of memory used.
const int FP_PREFIX_LEN = 4;

struct FieldMeta {
    int16_t tag;
    bool is_optional;
};

struct TypeSpec {
    TType ttype;
    uint8_t    fp_prefix[FP_PREFIX_LEN];

    // Use an anonymous union here so we can fit two TypeSpecs in one cache line.
    union {
        struct {
            // Use parallel arrays here for denser packing (of the arrays).
            FieldMeta* metas;
            TypeSpec** specs;
        } tstruct;
        struct {
            TypeSpec *subtype1;
            TypeSpec *subtype2;
        } tcontainer;
    };

    // Static initialization of unions isn't really possible,
    // so take the plunge and use constructors.
    // Hopefully they'll be evaluated at compile time.
    explicit TypeSpec(TType ttype) : ttype(ttype) {
        std::memset(fp_prefix, 0, FP_PREFIX_LEN);
    }

    TypeSpec(TType ttype,
                const uint8_t* fingerprint,
                FieldMeta* metas,
                TypeSpec** specs) :
                ttype(ttype)
    {
        std::memcpy(fp_prefix, fingerprint, FP_PREFIX_LEN);
        tstruct.metas = metas;
        tstruct.specs = specs;
    }

    TypeSpec(TType ttype, TypeSpec* subtype1, TypeSpec* subtype2) :
        ttype(ttype)
    {
        std::memset(fp_prefix, 0, FP_PREFIX_LEN);
        tcontainer.subtype1 = subtype1;
        tcontainer.subtype2 = subtype2;
    }
};

} // namespace local
} // namespace reflection
} // namespace dr
} // namespace pebble


#endif // PEBBLE_DR_REFLECTIONLOCAL_H

